CODEWITHSUNDEEP
bash
nowox
nowox

Reputation: 29066

Reopen STDOUT and STDERR after closing them?

In bash consider I did this stupid thing:

$ exec 1>&-
$ exec 2>&-

I am sure I have not yet lost the game (oops actually I lost The Game) and I can reconnect to stdout. The think is I don't know how.

First thing I tried is create a fifo and using another shell to monitor stdout of the first shell. It did not work, I don't know why:

tty1

$ mkfifo stdout
$ exec 1>stdout
$ echo "Hello stdout"

tty2

$ tail -f stdout
$ # nothing here

How can I reconnect my closed STDOUT and STDERR after all?

I know that a solution would be to save STDOUT before playing with it: 

$ exec 3>&1
$ exec 1>&-
$ echo "Nothing will see this"
$ exec 1<&3 # Restoring stdout

Upvotes: 9

Views: 4620

Answers (2)

Jay Bosamiya
Jay Bosamiya

Reputation: 3209

I am running this on an Ubuntu machine, so I am not sure if it'll work for you, but this is what I did:

$ exec 1>&0
$ exec 2>&0

Suddenly, I had STDOUT and STDERR reconnected. Magic!

Explanation: Running the following commands, we get the following output:

$ ls -l /dev/stdout
lrwxrwxrwx 1 root root 15 Jun 11 23:39 /dev/stdout -> /proc/self/fd/1

$ ls -l /proc/self/fd/1
lrwx------ 1 jay jay 64 Jun 22 01:34 /proc/self/fd/1 -> /dev/pts/10

$ ls -l /proc/self/fd/
total 0
lrwx------ 1 jay jay 64 Jun 22 01:35 0 -> /dev/pts/10
lrwx------ 1 jay jay 64 Jun 22 01:35 1 -> /dev/pts/10
lrwx------ 1 jay jay 64 Jun 22 01:35 2 -> /dev/pts/10
lr-x------ 1 jay jay 64 Jun 22 01:35 3 -> /proc/12224/fd

Since all three fd's point to the same thing, we can return them back to normal just by pointing to /dev/pts/10 which the exec 1>&0 and exec 2>&0 do

Upvotes: 8

rici
rici

Reputation: 241671

The simplest way, since you haven't closed stdin, which is also connected to your terminal:

exec 2>&0 1>&0

You could also use /dev/tty:

exec 2>/dev/tty 1>&2

You have to do that blind, since stderr is where bash echos what you type, and without stderr, it can't echo.

Upvotes: 6

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